Environmental Engineering Reference
In-Depth Information
manufacture of transformers and capacitors due to their ability to withstand exceptionally
high temperatures.
Investigation of this site began with a Phase I ESA that identified 25 RECs and 15 AOCs.
Three Phase II subsurface investigations were conducted to find and define the nature and
extent of contamination at the site. Investigative actions included drilling more than 80 soil
borings, installing temporary groundwater monitoring wells, and collecting and analyz-
ing more than 100 samples for selected compounds including DNAPL and LNAPL VOCs,
PAHs, SVOCs, PCBs, and heavy metals (As, Ba, Cd, Cr, Cu, Pb, Hg, Mg, Mn, Se, Ag, and
Zn). Figure 14.14 shows the locations of the RECs and AOCs.
This site is located in a geologically vulnerable area of shallow groundwater hydrauli-
cally connected and very close to a large surface water body (vulnerability rating = 71).
Luckily, a synergistic effect between a high-risk chemical released into a geologically
vulnerable area did not occur because this site did not use significant amounts of chemi-
cals. As a result, the extent of contamination did not extend more than 6 m (20 ft) beyond
release points and did not extend to depths greater than 1 m beneath the ground sur-
face. A geologic map would have helped predict this outcome, improved the soil and
groundwater sampling protocols, and would have also saved significant time and finan-
cial resources.
Of the several contaminants detected in soil, the only areas requiring remediation were
one impacted with PCBs and another impacted with lead. The area impacted with PCBs
was located near the transformer area (Figure 14.13). The area impacted with lead was
located beneath the facility's water tower painted with a lead-based paint removed by
weathering (Figure 14.13). Contaminants were detected in the shallow groundwater, but
not at levels requiring further action. The remedial option selected was excavation of
impacted soil. Excavation was selected since both impacted locations were accessible and
the contamination was shallow and restricted to the upper 1 m of soil. Remediation was
completed within 1 week. The total cost of investigation and remediation of this site was
$400,000 and was completed in 1 year from initiation of the Phase I ESA to closure by the
regulatory agency.
The lessons learned from this case study include
• Geologic maps are essential to all remediation efforts. In areas of vulnerable geol-
ogy and chemicals with low groundwater risk factors, geologic maps provide
valuable information that help guide investigative and remedial efforts.
• Applying urban investigative and geologic forensic techniques such as compre-
hensive site history and knowledge of contaminant fate and transport help to
increase the effectiveness of the remediation effort.
• A characterization of the fate and transport of lead and PCBs. Lead and PCBs had
been released at this facility and did not impact groundwater even though ground-
water was shallow (within 1 m of the surface). These substances also did not migrate
a significant distance laterally because of the nature of the compounds (high soil
contaminant risk factor) and the absence of anthropogenic pathways or disturbance.
• There is a lack of synergy at sites between chemicals and the geologic environ-
ment where chemicals with a high risk to groundwater were not used significantly
during the operational history of the facilities.
• Successful and cost-effective remediation is possible when no high-risk chemicals
are present. Modest environmental impacts and timely remediation can also be
achieved.
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